U.S. patent application number 10/662523 was filed with the patent office on 2005-03-17 for dual voltage circuit tester.
This patent application is currently assigned to SNAP-ON TECHNOLOGIES, INC.. Invention is credited to Johnson, Robert D., Mieczkowski, Daniel, Schaefer, Mark R..
Application Number | 20050057243 10/662523 |
Document ID | / |
Family ID | 34274121 |
Filed Date | 2005-03-17 |
United States Patent
Application |
20050057243 |
Kind Code |
A1 |
Johnson, Robert D. ; et
al. |
March 17, 2005 |
DUAL VOLTAGE CIRCUIT TESTER
Abstract
A handheld dual voltage circuit tester, method and electronic
circuit that quickly allows a technician to determine whether an
automotive electrical system runs on a 12-14 volt circuit or 36-42
volt circuit. The tester may be used for automobiles having a
single voltage electrical system, or automobiles with distinct
electrical systems operating on one of a 12-14 volts circuit or a
36-42 volt circuit. The tester includes a screwdriver-type
elongated handle and probe tip. The tester also includes electronic
circuitry disposed within its handle, heat shrink tubing, a
conductive spring assembly, a strain relief, a retractable coil
cord, a ground clip and insulation that encloses the ground clip.
The tester also includes electronic circuitry that emits light of a
first color when a 12-14 volt circuit is sensed, and light of a
second color when a 36-42 volt circuit is sensed.
Inventors: |
Johnson, Robert D.;
(Pleasant Prairie, WI) ; Schaefer, Mark R.;
(Greendale, WI) ; Mieczkowski, Daniel; (Pleasant
Prairie, WI) |
Correspondence
Address: |
MCDERMOTT, WILL & EMERY
600 13th Street, N.W.
Washington
DC
20005-3096
US
|
Assignee: |
SNAP-ON TECHNOLOGIES, INC.
|
Family ID: |
34274121 |
Appl. No.: |
10/662523 |
Filed: |
September 16, 2003 |
Current U.S.
Class: |
324/754.02 |
Current CPC
Class: |
G01R 1/06788 20130101;
G01R 19/16561 20130101 |
Class at
Publication: |
324/158.1 |
International
Class: |
G01R 001/00 |
Claims
1. A handheld circuit tester for an automotive electrical system
having circuit portions respectively operable at a first nominal
voltage range with respect to ground and a second nominal voltage
range with respect to ground, the tester comprising: an elongated,
curved handle portion, the handle portion being substantially in
the shape of a screwdriver handle; a probe device, substantially in
the shape of a screwdriver shank, the probe device coupled to the
handle portion and capable of contacting a circuit point of an
automotive circuit; a ground device coupled to the handle portion
and capable of being securely attached to a ground point; and
circuitry disposed within the handle portion and operatively
coupled to the probe device and the ground device, the circuitry
being configured to sense voltage at the circuit point and to
indicate whether the sensed voltage corresponds to the first or
second nominal voltage range.
2. The tester as recited in claim 1, wherein the circuitry includes
a first visible indicator that corresponds to a sensed voltage
within the first nominal voltage range, and a second visible
indicator that corresponds to a sensed voltage within the second
nominal voltage range.
3. The tester as recited in claim 2, wherein the first and second
visible indicators are light emitting devices.
4. The tester as recited in claim 3, wherein the handle portion is
composed of a material that is sufficiently transparent such that
the light emitting devices are visible through the material when
the light emitting devices are energized.
5. The tester as recited in claim 4, wherein the handle material is
a polymer.
6. The tester as recited in claim 3, wherein the first visible
indicator when active emits light of a first color, and the second
visible indicator when active emits light of a second color.
7. The tester as recited in claim 3, wherein the first and second
visible indicators each comprise two LEDs.
8. The tester as recited in claim 1, further comprising: a spring
assembly disposed within the handle between the probe device and
electronic circuit, wherein the spring assembly is comprised of a
conductive material, and wherein the spring assembly is configured
to compress when force is applied to the probe device.
9. The tester as recited in claim 1, wherein the ground device
includes insulation positioned thereon, and wherein the probe
device includes protective layer tubing positioned thereon, the
tubing being configured to securely fit over an exposed portion of
the probe device.
10. The tester as recited in claim 8, further comprising: a
retractable assembly that includes an insulated flexible electrical
wire, the retractable assembly being disposed between the spring
assembly and the ground device.
11. The tester as recited in claim 10, further comprising: a
protective cap having an open end capable of securely fitting over
at least a portion of the probe device, whereby the protective cap
protects the probe device from physical damage when the probe
device is not in use; and a strain relief device extending from the
handle, the strain relief device being coaxial with the handle and
the retractable assembly, wherein the retractable assembly has an
outside diameter and the strain relief device has an inside
diameter, wherein inside diameter of the strain relief device forms
a substantially annular ring around at least a portion of the
outside diameter of the retractable assembly.
12. The tester as recited in claim 2, wherein the circuitry
comprises: a first zener diode having a breakdown voltage
sufficient to energize only the first visible indicator when a
voltage corresponding to the lower nominal voltage range is sensed;
and a second zener diode having a breakdown voltage sufficient to
energize the second visible indicator when a voltage corresponding
to the higher nominal voltage range is sensed.
13. A method for testing the voltage level of an automotive circuit
with a circuit tester, the automotive circuit having portions
respectively operable at a first nominal voltage level with respect
to ground and a second nominal voltage level with respect to
ground, the circuit tester including an elongated curved handle
portion, a probe device substantially in the shape of a screwdriver
shank, a ground device, and electronic circuitry operatively
coupled to the probe device and the ground device, the electronic
circuitry being disposed within the handle portion, wherein the
circuitry is configured to sense a voltage at a circuit point of an
automotive circuit, and wherein the circuit tester further includes
a visible display operatively coupled to electronic circuitry, the
handle being composed of a material that is sufficiently
transparent such that the visible display is visible through the
handle, the method comprising the steps of: connecting the probe
device to a circuit point of an automotive circuit; connecting the
ground device to ground; and determining whether the voltage at the
circuit point corresponds to the first or second nominal voltage
level based on the visible display.
14. The method as recited in claim 13, wherein the visible display
includes a first visible indicator that corresponds to a sensed
voltage at the first nominal voltage level, and a second visible
indicator that corresponds to a sensed voltage at the second
nominal voltage level.
15. The method as recited in claim 14, wherein the first visible
indicator includes an LED that emits light of a first color when
active, and the second visible indicator includes an LED that emits
light of a second color when active.
16. An electrical circuit for testing the voltage level of an
automotive circuit, the electrical circuit being adapted to be
disposed within a curved, elongated handle of a circuit tester for
automotive electrical circuits, the handle being composed of a
material that is sufficiently transparent such that light from a
first light emitting load and light from a second light emitting
load are visible through the handle, the circuit comprising: a
first voltage sensing device that senses a nominal low level
automotive system voltage with respect to ground; a second voltage
sensing device that senses a nominal high level automotive system
voltage with respect to ground; wherein the first light emitting
load is responsive to the first voltage sensing device to be
energized when the nominal low level automotive system voltage is
sensed; and the second light emitting load is responsive to the
second voltage sensing device to be energized when the nominal high
level automotive system voltage is sensed.
17. The circuit as recited in claim 16, wherein the first light
emitting load is a set of series-connected LEDs, and the second
light emitting load is a set of series-connected LEDs.
18. The circuit as recited in claim 17, wherein the first set of
series-connected LEDs emits light of a first color when energized
and the second set of series-connected LEDs emits light of a second
color when energized.
19. The circuit of claim 16 wherein the first voltage sensing
device comprises a zener diode, and the second voltage sensing
device comprises a zener diode.
20. An electrical circuit for testing the voltage level of an
automotive circuit, the circuit comprising: a first zener diode
configured to energize a first visible indicator; a second zener
diode configured to energize a second visible indicator; wherein
the first visible indicator is responsive to the first zener diode
such that the first visible indicator provides a visible indication
that a low automotive system voltage is sensed, and wherein the
first zener diode has a breakdown voltage sufficient to energize
only the first visible indicator when a low automotive system
voltage is sensed; and wherein the second visible indicator is
responsive to the second zener diode such that the second visible
indicator provides a visible indication that a high automotive
system voltage is sensed, and wherein the second zener diode has a
breakdown voltage sufficient to energize the second visible
indicator when a high automotive system voltage is sensed.
21. An apparatus for testing the voltage level of an automotive
circuit having circuit portions respectively operable at a low
nominal voltage range with respect to ground and a high nominal
voltage range with respect to ground, the apparatus comprising:
means for sensing an automotive system voltage in the low nominal
range; means for providing a first visible indicator when a low
automotive system voltage is sensed; means for sensing an
automotive system voltage in the high nominal range; and means for
providing a second visible indicator when a high automotive system
voltage is sensed.
Description
FIELD OF THE DISCLOSURE
[0001] The present disclosure relates to voltage testers, and more
particularly to efficiently determining whether an automotive
electrical system operates at 12-14 volts or 36-42 volts.
BACKGROUND OF THE DISCLOSURE
[0002] Electrical circuit testers are well known in the art, and
are commonly used by electricians as well as laypersons. Such
testers are also used by automotive technicians to determine the
voltage at which an automotive electrical system operates. Until
recent years, automotive electrical systems typically incorporated
a power supply of 6-12 volts, generally through a battery.
Accordingly, a 6-12 volt circuit tester was used to determine the
voltage level of power supplied to these systems. This type of
circuit tester had a screwdriver-type design and included a light
bulb. The tester was designed so that the light bulb would become
brighter as the sensed voltage increased.
[0003] Today, a demand has emerged for a higher number and
sophistication of electrical vehicular features. Types of vehicular
features which may require greater power are electrically heated
seats, entertainment systems, navigation systems, heated
windshields, pre-heated catalytic converters, brake-by-wire
systems, electronically-controlled valves and air conditioning
systems, just to name a few. Because the greater number and
sophistication of features generally require a greater amount of
power, a higher demand has accordingly emerged for vehicles with a
larger electrical power supply.
[0004] Because this higher level of power could be supplied with
increased voltage, e.g., 36-42 volts, automotive manufacturers
began to consider how they could implement automotive electrical
systems that supported this higher power supply. Implementation of
greater power supplies has been proposed generally through one of
two means. Some automobile manufacturers, such as BMW (also known
as Bavarian Motor Works), have proceeded to implement a higher
voltage power supply system of 36 volts. The entire electrical
system of such automobiles operates at 36 volts to 42 volts or
higher. However, implementation of this higher 36-42 volt system
requires that all electrical components used within the system
support the higher voltage.
[0005] These higher voltage systems can be expensive and relatively
complex when compared to the traditional 12-14 volt systems.
Greater power supplies were generally more expensive, and the
manufacturer would be required to pass this cost on to the
consumer. By substantially increasing the prices of its vehicles, a
manufacturer risked losing customers.
[0006] Moreover, the complexity of such systems required a
re-design of automotive electrical systems so that they could
support these higher voltages. Delaying the introduction of a
higher voltage electrical system to wait for a re-design meant
delaying the introduction of a greater number and sophistication of
features. The manufacturer risked losing customers because the
customer demanded such features. Accordingly, in lieu of full
implementation of the higher voltage systems, some automobile
manufacturers have proposed a more gradual transition. This more
gradual approach has been in the form of a dual voltage system that
operates in both the lower 12-14 volt range as well as the 36-42
volt range.
[0007] Implementation of dual voltage systems allows the automobile
manufacturers flexibility in that they need not delay the
introduction of features requiring a higher power supply until such
time as the electrical components or re-designs are available that
support these higher power supplies. Typically, dual voltage
systems require two battery systems which power different
subsystems of the electrical system. Due to these dual voltage
systems, an automotive technician must determine which portions of
the electrical system operate in the 12-14 volt range, and which
portions operate within the higher 36-42 volt range.
[0008] Determination of the appropriate voltage level is often
essential to proper repair of a vehicle. Because of these dual
12-{fraction (14/36)}-42 voltage systems, it is desirable to have a
circuit tester that can inform the technician as to which voltage
level an automotive electrical system operates. Moreover, because
all components of a particular automobile's electrical system might
operate at either a higher voltage of 36-42 volts or a lower
voltage of 12-14 volts, it is desirable to know the voltage level
on which the system operates.
[0009] There is a need for an automotive circuit tester and method
that provide an efficient way to determine an automobile's power
supply voltage, and addresses the issues associated with the
emergence of higher power supply systems.
SUMMARY OF THE DISCLOSURE
[0010] The present disclosure addresses the needs noted above by
providing an efficient way of determining the voltage at which an
automotive electrical system operates.
[0011] In one aspect of the present disclosure, a circuit tester is
provided for testing automotive electrical systems. The circuit
tester includes a curved handle portion that can be easily gripped
by a technician, a screwdriver-type probe tip designed to contact
the hot or positive side of an automotive circuit, and a ground
clip designed to contact the negative side of an automotive
circuit. The handle portion and the probe tip are substantially
similar in size, shape and form to a regular heavy-duty
screwdriver, that is visible to the technician while testing a test
circuit. This is because the handle portion is composed of a
material that is sufficiently transparent such that light from the
LEDs may be viewed through the material.
[0012] The tester further includes electrical circuitry that is
operatively coupled to the probe tip. This circuitry is configured
to sense a low automotive system voltage of about 12-14 volts, as
well as a high automotive system voltage of 36-42 volts. These
voltages are measured according to the voltage drop between the
probe tip and the ground clip, with ground being the reference
point from which the voltage drop is measured. The circuit provides
a visible display that informs the technician as to the voltage
level of the automobile by emitting light of a first color when a
low automotive system voltage is sensed, and light of a second
color when a high automotive system voltage is sensed. The tester
also includes safety features such as heat shrink tubing, a strain
relief and an insulator boot. The heat shrink tubing or protective
layer covers the probe tip and protects a portion of the probe tip
from exposure. The strain relief protects the wiring within the
tester from being damaged, thus reducing the risk of exposed wires
and therefore, user injury. The insulator boot insulates the ground
clip so that it, too, is not unnecessarily exposed. However, the
insulator boot does not interfere with operation of the ground
clip. The tester also includes a retractable coil cord for ease of
stowing and a cap that protects the probe tip when the tester is
not in use.
[0013] In another aspect of the present disclosure, a method is
provided for testing the voltage of an automotive electrical
system. The method is implemented using the tester hereinabove. The
method includes connecting the probe tip to the positive side of an
automotive circuit, connecting the ground clip to the negative side
of an automotive circuit, and determining the voltage level of the
automotive circuit based on the indicators on the visible display.
The visible display emits light of a first color when a low
automotive system voltage is sensed, and light of a second color
when a high automotive system voltage is sensed.
[0014] In yet another aspect of the present disclosure, an
electrical circuit is provided. The electrical circuit is
relatively inexpensive, requiring few components. In this
embodiment, the electrical components include a first voltage
sensing device that senses a low automotive system voltage, and a
second voltage sensing device that senses a high automotive system
voltage.
[0015] The circuit further includes a first set of series-connected
LEDs. When the first voltage sensing device turns on at about 10
volts, it energizes the first set of series-connected LEDs, thereby
providing a visible indication to the technician of a 12-14 volt
circuit. A second set of series-connected LEDs are responsive to
the second voltage sensing device. When the second voltage sensing
device turns on at about 34 volts, it energizes the second set of
series connected LEDs, thereby providing a visible indication that
a 36-42 volt is being sensed. These sensing devices are designed to
sense voltages of 10 and 34 volts, which are lower than the 12-14
volt or 36-42 volts that would generally apply to an automotive
electrical system. The relatively low voltage sensitivity of the
sensing devices takes into account situations where a battery is
low or a heavy load is applied to the electrical system. The
circuit includes a number of resistors which impede the flow of
current to the electronic circuit, especially the diodes, thus
protecting against overdriving the diodes and burning them out.
[0016] One advantage of the present disclosure is to provide an
easy-to-use, handheld circuit tester and method that assists a
technician in quickly determining the voltage level at which an
automotive electrical system operates.
[0017] Another advantage of the present disclosure is to provide a
circuit tester that incorporates safety features due to the
inherent risks associated with humans being in close proximity with
live electrical wires.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] These and other objects, features, and characteristics of
the present disclosure will become apparent to one skilled in the
art from a close study of the following detailed description in
conjunction with the accompanying drawings and appended claims, all
of which form a part of this application. In the drawings:
[0019] FIG. 1A is a top view of a dual voltage circuit tester in
accordance with one embodiment of the present disclosure.
[0020] FIG. 1B is a perspective view of an alternative
screwdriver-type probe tip in accordance with one embodiment of the
present disclosure.
[0021] FIG. 2 is an illustration of the dual voltage circuit tester
during a test of an automotive electrical circuit in accordance
with one embodiment of the present disclosure.
[0022] FIG. 3 is an electrical schematic for an electronic circuit
for an automotive circuit tester in accordance with one embodiment
of the present disclosure.
DETAILED DESCRIPTION OF THE DISCLOSURE
[0023] The present disclosure relates to a tester, circuit and
method for testing the voltage level of an automotive electrical
circuit. The substantially screwdriver-shaped tester allows a
technician to promptly determine whether the technician is testing
a 12-14 volt circuit or a 36-42 volt circuit. This voltage level
determination is made based on the color of light emitting diodes
on the tester's visual display. A blue light emitting diode
indicates a voltage of 12-14 volts is being sensed, while both red
and blue light emitting diodes indicate a voltage level of 36-42
volts is being sensed. At times, the voltage drop of about 12-14
volts is hereinafter referred to as a low automotive system
voltage, while the voltage drop of about 36-42 volts is hereinafter
at times referred to as a high automotive system voltage. These
voltage drops are measured with reference from the positive side of
an automotive electrical circuit to the negative side of the same
electrical circuit.
[0024] The voltage ranges of 12-14 volts and 36-42 volts take into
account the difference between the power supplied to these
electrical systems and the actual operating voltage of these
electrical systems with reference to charging voltages. For
example, when a 36 volt power supply is applied to an automotive
electrical system, the actual operating voltage with respect to the
charging voltage might be closer to 42 volts and sometimes
higher.
[0025] The present disclosure is described with reference to
testing voltage levels of automotive systems. The embodiments
described herein may include or be used with any appropriate
voltage source, such as a battery, an alternator and the like,
providing any appropriate voltage. Although the embodiments
described herein make particular reference to automobile systems
which may include cars, trucks, SUVS, and other vehicles on wheels
which incorporate 12-14 or 36-42 volt electrical systems, it should
be understood that the systems may be incorporated into other
devices, such as boats, ships, motorcycles, generators and
airplanes. The embodiments of the tester, circuit and method
described in the present disclosure are useful for applications
that incorporate DC low voltage systems.
[0026] Referring now to FIG. 1A, illustrated is a top view of a
handheld voltage tester 100 in accordance with one embodiment of
the present disclosure. Because the tester 100 is handheld, its
portability makes it particularly suitable as a circuit tester for
an automotive circuit and circuits for vehicles generally. The
tester includes a handle 105, cap 110, probe tip 115, heat shrink
tubing 120, a spring assembly 125, strain relief 130, a retractable
coil cord 135, an insulator boot 140, a ground clip 145 and a PCB
subassembly 150.
[0027] The tester 100 of the present disclosure is easy to use. The
handle 105 and probe tip 115 are substantially the shape and size
of a heavy-duty screwdriver. The length L of handle 105 is indented
and/or curved so that a technician may easily grip the handle 105
of the circuit tester 100 when testing an automotive circuit. The
curved portion is substantially in the shape of an elongated "S".
The end of the handle 105 nearest the heat shrink tubing 120 is
wide so that the user's hand does not slip from the handle 105. The
wide end of handle 105 also provides protection by stopping the
user's hand from coming too close to the probe tip 115 where a live
voltage might be measured. The circumference of handle 105 is
furrowed or grooved for ease of gripping. The handle 105 is
composed of a material that is sufficiently transparent so that
LEDs on the PCB subassembly 150 are visible to the technician when
the tester is in operation. Examples of materials of sufficient
transparency include any polymer material available in transparent
grades, such as polycarbonate, acrylic, nylon, cellulose acetate,
cellulose butyrate, among others. The materials are listed in
approximately increasing order of solvent resistance which is an
important consideration for durability in products used in the
automotive garage environment. As viewed through the polymer, the
LEDs provide a visual indication or indications of the voltage
level being tested as set forth in greater detail hereinbelow.
Alternatively, or in addition to the transparent material, the
handle may include openings 170, 175, 180, 185 through which LEDs
may be viewed.
[0028] The probe tip 115 is made of a conductive material such as a
steel alloy or other suitable material. The probe tip 115 is
designed for connection with wires and contacts in an automotive
electrical circuit. The probe tip 115 is similar in form, shape and
size to a heavy duty screwdriver tip or shank. A screwdriver shank
is generally used by a technician for insertion into a slot or
recess located in the head of a screw. In the embodiment shown, the
probe tip 115 is of a length similar to a screwdriver shank, and
the end of probe tip 115 is pointed.
[0029] Alternatively, the screwdriver shank may be generally thin
and wedge-shaped as shown in FIG. 1B. This screwdriver-type
configuration is suitable for the tester 100 because it allows the
wide side of probe tip 115 to be flatly placed against an
automotive test circuit, thereby making the tester 100 easier to
use and providing for better electrical flow from the automotive
test circuit into the tester 100.
[0030] Alternatively, or in addition to the thin, wedge shape
illustrated in FIG. 1B, screwdriver shanks are also commonly fluted
with grooves or furrows such as with a Philips screwdriver.
Accordingly, a fluted embodiment for the probe tip 115 would also
make it suitable for contacting electrical wires since the wire to
be tested may be positioned into the groove of such a fluted
screwdriver-type probe tip.
[0031] The spring assembly 125 provides two functions. One
advantage of the spring assembly 125 is that it acts as an
electrical conductor. The spring assembly 125 may be made of a
conductive material such as a steel alloy, copper, or any other
suitable material. Another advantage of the spring assembly 125 is
that it acts as a compression device. In this respect, the spring
assembly 125 protects the electronic circuitry on the PCB
subassembly 150 within the handle 105 by providing a barrier for
force that might be relayed to the circuitry. Such force might be
relayed, for example, when the probe tip 115 is placed into a test
circuit.
[0032] The heat shrink tubing 120 is plastic tubing that has been
heated and shrink-fitted over the probe tip 115. Heat shrink tubing
120 decreases the amount of conductive material of probe tip 115
that is exposed. Because of the potentially hazardous level of
voltage that the probe tip 115 measures, heat shrink tubing 125
acts as a protective feature against conduction to objects other
than the probe and its circuitry. In lieu of heat shrink tubing,
any suitable protective layer may be positioned on the probe tip
115 to act as a protective feature.
[0033] Strain relief 130 is coaxial with handle 105 and retractable
coil cord 135. Strain relief 130 extends from handle 105 and forms
a substantially annular ring around retractable coil cord 135.
Strain relief 130 protects the circuitry on the PCB subassembly 150
from experiencing undue stress, torsion and deformation, thus
reducing the likelihood that the circuitry contained therein will
be damaged. The circuitry could experience undue stress, torsion or
deformation if, for example, the tester 100 was used with a
technician handling the cord 135 as opposed to the handle 105. The
force applied to the wiring of the cord 135 after prolonged use
could cause the electrical wires inside cord 135 to be damaged. If
the wires are damaged, the tester 100 could malfunction. Moreover,
the wires could become exposed through the insulated covering of
cord 135, thus increasing chances of user injury. The inside
diameter of strain relief 130 is larger the outside diameter of
retractable coil cord 135 so that it does not rub against or abrade
cord 135.
[0034] Ground clip 145 is used as a connection to the ground of the
circuit being tested. Ground is the reference point from which a
voltage drop is measured. Ground clip 145 is encased and surrounded
by insulator boot 140, which provides protection against the
undesired flow of current from the test circuit from the tester 100
to the technician or other objects. Insulator boot 140 is made of
any suitable material that is both heat resistant as well as
electrically resistant. Ground clip 145 extends from the inside
diameter insulator boot 140 a sufficient amount such that insulator
boot 140 need not be removed from ground clip 145 in order for
ground clip 145 to properly contact and ground the test
circuit.
[0035] Retractable coil cord 135 is a flexible wire, the
circumference of which is enclosed by insulation. Like insulator
boot 140, the insulation may be of any suitable material. The
retractable coil cord 135 permits the cord to be retracted, and
therefore, stowed away easily when the tester 100 is not in use,
and lengthened when the tester 100 is in use. The coil--and
accordingly, the coil cord--should be sufficiently long such that
the hot side of any portion of an automotive circuit can be reached
with one end, and that the negative side of that circuit can be
reached with the end of the tester 100 that supports the ground
clip 145.
[0036] Wire 160 connects the wiring of the retractable coil cord
135 and the circuitry of the PCB subassembly 150. The retractable
coil cord 135 extends from the circuitry to ground clip 145, thus
extending to an electrical ground. This wire 160 is stripped and
soldered to the PCB subassembly 150. Wire 155 connects the spring
assembly 125 and the PCB subassembly 150. This wire 155 is soldered
to the PCB subassembly 150.
[0037] The tester 100 obtains its power from the test circuit.
Accordingly, no battery or other power supply is included with the
tester 100. Nor is a power switch included.
[0038] The circuitry (not shown) for the tester 100 is mounted onto
a printed circuit board (PCB) subassembly 150. A schematic for the
circuitry on the PCB subassembly is illustrated and described in
greater detail in connection with FIG. 3.
[0039] Referring now to FIG. 2, illustrated is a perspective view
of the dual voltage circuit tester 300 during a test of an
automotive electrical circuit 310 in accordance with one embodiment
of the present disclosure. Circuit 310 is tested by connecting the
circuit tester 300 to the automotive electrical circuit 310 while
observing proper polarity, which is known in the art. Generally,
the probe tip 315 should contact the positive or "hot" side 330 of
the wiring for an automotive circuit 310. Heat shrink tubing 325
decreases the amount of conductive material of probe tip 315 that
is exposed. The automotive circuit may reside in a wiring harness,
lighting system, starter, solenoid, brake light, electrical motor,
power steering pump or any other electrical system resident in an
automobile. The ground clip 340 should be connected to the circuit
ground or negative side 320 of the same automotive circuit 310.
[0040] The tester 300 may be held by the technician in a manner
similar to the way in which a pencil or fork is held. Visible
indicator LEDs 350, 360 emit light of a first color in the visible
spectrum when the circuitry on PCB subassembly 150 senses a low
automotive system voltage, thereby providing a visible indication
to the technician of a 12-14 volt circuit. The LEDs 350, 360 are
located on two sides of handle 105 so that they can be viewed
easily by the technician. LEDs 350, 360 are substantially
simultaneously energized, so that they create an illusion of a
single light when viewed by the technician.
[0041] Visible indicators 370, 380 emit light of a second color in
the visible spectrum when the circuitry senses a high automotive
system voltage, thereby providing a visible indication to the
technician of a 36-42 volt circuit. The LEDs 370, 380 are located
on two sides and at one end of handle 105 so that they can be
viewed easily by the technician. LEDs 370, 380 are substantially
simultaneously energized, so that they create an illusion of a
single light when viewed by the technician.
[0042] Although LEDs 350, 360, 370, 380 are located on two sides
and at both ends of the PCB subassembly 150 as viewed on handle 105
in this embodiment, it should be understood that the LEDs 350, 360,
370, 380 can be located at any point such that they may be viewed
by the technician. Similarly, the number of LEDs is not limited to
two. The tester 100 may include one or more LEDs or other visible
indicators for each voltage level sensed. Moreover, the LEDs for
low automotive voltages 350, 360 and the LEDs for high automotive
system voltages 370, 380 need not be of a different color. The
handle 105 could simply include markings that indicate which
voltage level is being sensed.
[0043] Referring now to FIG. 3, illustrated is an electrical
schematic 200 of a circuit for a circuit tester in accordance with
one embodiment of the present disclosure. The circuit 200 includes
a first resistor 205 coupled in parallel to a second resistor 220.
The resistance of resistors 205, 220 is 2.43 kilo-ohms. The
resistors are designed in parallel to effect a total resistance
between about 1.215 kilo-ohms. Light emitting diodes 210, 215 are
connected in series with resistor 205 and resistor 220. These
diodes 210, 215 emit light in the blue range when a breakdown
voltage of 10 volts is reached. The 10 volts is, of course, lower
than the 12-14 volts indicated as sensed by the circuit 200. The
lower breakdown voltage of diode 225 compensates for situations
when an automotive battery is low, a common situation in an
automobile diagnosed with problems. Moreover, voltage will drop
slightly when heavy loads are applied to the battery. A common
example of a heavy load application is when an automotive starter
is energized.
[0044] Moving now to the other end of the circuit 200, resistors
230, 235, 240 are each 1.21 kilo-ohms. Light emitting diodes 245,
250 emit light in the red spectrum when a breakdown voltage of 34
volts is sensed by the tester. The 34 volts is, of course, lower
than the 36-42 indicated as sensed by the circuit 200. The lower
breakdown voltage of diode 255 accounts for situations when an
automotive battery is low, a common situation in an automobile
diagnosed with problems. Moreover, voltage will drop slightly when
heavy loads are applied to the battery. A common example of a heavy
load occurrence is when an automotive starter is energized.
[0045] Wiring at connection 265 connects the wiring of the
retractable coil cord and the circuitry of the PCB subassembly. The
retractable coil cord extends from the circuitry to ground clip,
thus extending to an electrical ground. Wiring at connection 265 is
stripped and soldered to the PCB subassembly.
[0046] Connection 260 connects the spring assembly and the PCB
subassembly. Wiring at connection 260 is soldered to the PCB
subassembly. Because the conductive spring assembly also contacts
the probe tip, current is conducted from the probe tip to the PCB
subassembly via the conductive spring assembly.
[0047] When the tester senses a closed circuit of 12-14 volts,
current flows through resistors 205, 220, light emitting diodes
210, 215 and zener diode 225. Zener diode 225, being a reverse
biased semiconductor diode, is designed to experience a large,
abrupt rise in electrical current in the presence of a small
voltage. Because zener diode 225 has a breakdown voltage of about
10 volts (in reference from probe tip to ground), this diode 225
turns on when it reaches this breakdown voltage. If the voltage is
lower than around 10 volts, zener diode 225 will not turn on. When
the zener diode 225 turns on, light emitting diodes 210, 215 are
energized, and they emit a blue light which indicates that the
probe is detecting a 12-14 volt circuit.
[0048] When the tester's probe tip of the tester detects a voltage
of 34 volts or more, current flows through essentially the entire
circuit, including resistors 205, 220, 230, 235, 245 as well as
light emitting diodes 210, 215, 245, 250 and zener diodes 225, 255.
At this point, zener diode 255 turns on due to its breakdown
voltage being reached at approximately 34 volts (in reference from
probe tip to ground). When zener diode 255 turns on, light emitting
diodes 245, 250 are energized, thereby emitting a red light which
indicates that the probe is detecting a 36-42 volt circuit. Light
emitting diodes 210, 215 are also energized due to zener diode 225
having reached its breakdown voltage. As disclosed hereinabove,
light emitting diodes emit a blue light, thus indicating the
sensing of at least the lower voltage level of 12-14 volts.
[0049] The voltage tester, circuit and method have been described
with reference to certain exemplary embodiments. However, it will
be readily apparent to those skilled in the art that it is possible
to embody the tester circuit and method in forms other than these
embodiments. This may be done without departing from the spirit of
the disclosure. The embodiments are merely illustrative and should
not be considered restrictive in any way. The scope of the tester,
circuit and method are given by the appended claims, rather than
the preceding description, and all variations and equivalents that
fall within the range of the claims are intended to be
embraced.
* * * * *